Have you ever heard the phrase "straw that broke the camel's back"? I'm going to assume that you have, and if you haven't you can Google it.
Anyways imagine you're a happy little office building, doing what happy little office building do. You have two really tall neighbors, and all of you are good friends. One sunny, clear morning you see a plane in the distance going a bit lower than usual, but you think nothing about it.
Then, suddenly, HOLY FUCKING SHIT the plane slams head first into one of your neighbors. You're fine for the moment, but your neighbor looks badly hurt. You and your other neighbor try to console him for a while, but then FUCK FUCK FUCK another goddamn plane hits your other neighbor. Once again you're ok for the most part, some damage here and there but nothing major.
At this point you're pretty fucking scared; what if a plane hits you? You're sitting there worrying when all of a sudden WHAT IN THE EVER LOVING FUCK your buddy just collapses into a pile of rubble! Fucking gigantic pieces of metal and burning material slam into you. You're badly hurt now: you're on fire, huge pieces of you are gone, but you think you'll make it. The shock from the first building going down has barely passed when JESUS TITTY FUCKING CHRIST your other friend goes down. Once again large pieces of metal and burning shit slam into you with no mercy. You're really badly hurt now; there's a really big gash in your side and a really fucking hot fire raging inside you.
Hours pass and the fire burns on. Your steel beams aren't melting, but they are buckling under the intense heat of the inferno. What isn't helping the matter is the fact that large pieces of you are missing, thus transferring the load onto the already damaged and weakened beams. The fire burns and burns, and the beams get weaker and weaker. Eventually they get so weak that they can't hold up your weight anymore, and the floors above come crashing down. In the span of a few seconds you, along with all your hopes and dreams, are nothing more than a pile of rubble.